Dissemination of multidrug resistant bacteria to the polar environment - Role of the longest migratory bird Arctic tern (Sterna paradisaea).

The ever-increasing prevalence of antibiotic-resistant bacteria(ARB), primarily due to the frequent use and misuse of antibiotics, is an issue of serious global concern. Migratory birds have a significant role in dissemination of ARB, as they acquire resistant bacteria from reservoirs and transport them to other environments which are relatively less influenced by anthropogenically. We have investigated the prevalence of ARB in a long-distance migratory bird, the Arctic tern (Sterna paradisaea) captured from the Svalbard Archipelago. The birds were tagged with geolocators to track their extraordinary long migration, and the cloacal samples were collected before the migration and after the migration by recapturing the same birds. The tracking of 12 birds revealed that during the annual cycle they underwent a total of 166 stopovers (11-18, mean = 3.8) and recovery points along the Atlantic Ocean. Twelve major bacterial genera were identified from Arctic tern cloacal samples, which are dominated by Staphylococcus spp. and Aerococcus spp. The bacterial isolates showed resistance against 16 antibiotics (before migration) and 17 antibiotics (after migration) out of 17 antibiotics tested. Resistance to ß-lactam and quinolone class of antibiotics were frequent among the bacteria. The study highlights the potential role of Arctic tern in the dissemination of multidrug resistant bacteria across far and wide destinations, especially to the polar environments.

Total nitrogen influence bacterial community structure of active layer permafrost across summer and winter seasons in Ny-Ålesund, Svalbard.

The permafrost in the polar regions is vital for maintaining the status quo of the earth's climate by limiting greenhouse gas emissions. The present study aims to investigate the seasonal variations and the influence of physicochemical parameters on the bacterial diversity and community structure of active layer permafrost (AL) around Ny-Ålesund, Svalbard. The AL soil samples were collected from four different geographical locations around Ny-Ålesund during the winter and summer seasons. The 16S rDNA amplicon sequencing was carried out to investigate the diversity and distribution profiles of bacterial communities among the collected AL samples. Physico-chemical parameters including soil pH, moisture content, total carbon (TC), total nitrogen (TN), and trace metals concentrations were measured. Bacterial phyla, Proteobacteria (15.4%-26%) and Chloroflexi (9.6%-22.5%) were predominantly distributed across both seasons. In the winter samples, Verrucomicrobiota (14.12%-23.39%) phylum, consisting of genera Chthoniobacter and Opitutus were highly abundant (Lefse, p < 0.05), whereas in summer bacterial genera belonging to Gemmatimonadota (3.3%-13.74%) and Acidobacteriota (18.02%-28.52%) phyla were highly abundant. The bacterial richness and diversity index were not significantly different between the winter and summer seasons. Principal coordinate analysis (PCoA) has revealed a distinct grouping between two seasons (PERMANOVA, p < 0.05). Bacterial community structure was significantly varied between winter and summer seasons, whereas the physico-chemical variable, TN, influenced the community structure. About 37.8% of the total operational taxonomic units (OTUs) were shared between seasons, whereas 25.4% and 36.8% of OTUs were unique to the summer and winter seasons. The present study revealed that the conditions prevailing during winter and summer has shaped bacterial community structure in AL samples albeit the stable diversity and most of the variation was explained by TN, indicating its critical role in oligotrophic permafrost.

Impact of anthropogenic organic matter on bacterial community distribution in the continental shelf sediments of southeastern Arabian Sea.

The objective of this study was to understand the influence of anthropogenic organic matter on the spatial distribution microbial community in the continental shelf sediments of the Southeastern Arabian Sea (SEAS). The sediment samples were taken from the inner shelf (30 m depths) and outer shelf (100-200 m). The C:Nmolar ratio of the sediment displayed a significant variation between the inner and outer shelf and a higher terrestrial organic input in the inner shelf. Microbial community composition also showed a significant variation between the inner and outer shelf (p ≤ 0.05). Proteobacteria was the dominant phylum in the outer shelf sediments (42.5%), whereas Desulfobacterota (21.9%) was the dominant phylum in the inner shelf. Complex terrestrial organic matter degrading bacteria dominated the inner shelf, whereas oligophilic microbial community and autochthonous organic matter utilizing bacteria dominated the outer shelf. Thus the source of organic matter controlled the microbial distribution in the SEAS.

Bacterial community structure and functional profiling of high Arctic fjord sediments.

Kongsfjorden, an Arctic fjord is significantly affected by the glacier melt and Atlantification, both the processes driven by accelerated warming in the Arctic. This has lead to changes in primary production, carbon pool and microbial communities, especially that in the sediment. In this study, we have examined the bacterial community structure of surface (0-2 cm) and subsurface (3-9 cm) sediments of Kongsfjorden using the high throughput sequencing analysis. Results revealed that bacterial community structure of Kongsfjorden sediments were dominated by phylum Proteobacteria followed by Bacteroidetes and Epsilonbacteraeota. While α- and γ-Proteobacterial class were dominant in surface sediments; δ-Proteobacteria were found to be predominant in subsurface sediments. The bacterial community structure in the surface and subsurface sediments showed significant variations (p ≤ 0.05). Total organic carbon could be one of the major parameters controlling the bacterial diversity in the surface and subsurface sediments. Functional prediction analysis indicated that the bacterial community could be involved in the degradation of complex organic compounds such as glycans, glycosaminoglycans, polycyclic aromatic hydrocarbons and also in the biosynthesis of secondary metabolites.

Influence of environmental factors on benthic nitrogen fixation and role of sulfur reducing diazotrophs in a eutrophic tropical estuary.

Benthic nitrogen fixation in the tropical estuaries plays a major role in marine nitrogen cycle, its contribution to nitrogen budget and players behind process is not well understood. The present study was estimated the benthic nitrogen fixation rate in a tropical estuary (Cochin) and also evaluated the contribution of various diazotrophic bacterial communities. Nitrogen fixation was detected throughout year (0.1-1.11 nmol N g-1 h-1); higher activity was observed in post-monsoon. The nifH gene abundance was varied from 0.8 × 104 to 0.6 × 108 copies g-1dry sediment; highest was detected in post-monsoon. The Cluster I and Cluster III were the dominant diazotrophs. Sulfur reducing bacterial phylotypes (Deltaproteobacteria) contributed up to 2-72% of total nitrogen fixation. These bacteria may provide new nitrogen to these systems, counteracting nitrogen loss via denitrification and anammox. Overall, the study explained the importance of benthic nitrogen fixation and role of diazotrophs in a monsoon influenced tropical estuarine environments.

Abundance and diversity of diazotrophs in the surface sediments of Kongsfjorden, an Arctic fjord.

Diazotrophy in the Arctic environment is poorly understood compared to tropical and subtropical regions. Hence in this study, we report the abundance and diversity of diazotrophs in Arctic fjord sediments and elucidate the role of environmental factors on the distribution of diazotrophs. The study was conducted during the boreal summer in the Kongsfjorden, an Arctic fjord situated in the western coast of Spitsbergen. The abundance of nifH gene was measured through quantitative real-time PCR and the diversity of diazotrophs was assessed by nifH targeted clone library and next generation sequence analysis. Results revealed that the abundance of nifH gene in the surface sediments ranged from 2.3 × 106 to 3.7 × 107 copies g- 1. The δ-proteobacterial diazotrophs (71% of total sequence) were the dominant class observed in this study. Major genera retrieved from the sequence analysis were Desulfovibrionaceae (25% of total sequence), Desulfuromonadaceae (18% of total sequence) and Desulfobacteriaceae (10% of total sequence); these are important diazotrophic iron and sulfur-reducing bacterial clade in the Kongsfjorden sediments. The abundance of nifH gene showed a significant positive correlation TOC/TN ratio (r2 = 0.96, p ≤ 0.05) and total organic carbon (p ≤ 0.05) content in the fjord sediments. The higher TOC/TN ratio (4.24-14.5) indicated low nitrogen content organic matter in the fjord sediments through glacier runoff, which enhances the abundance and diversity of nitrogen fixing microorganisms.

Diversity of sediment associated Planctomycetes and its related phyla with special reference to anammox bacterial community in a high Arctic fjord.

The fjords of west Spitsbergen Svalbard, Arctic Norway, are undergoing a transformation as the impact of nutrient rich warmer Atlantic water is significantly altering the primary production and subsequently the carbon pool. Members of the phylum Planctomycetes are ubiquitous in marine systems and are important in the mineralization of organic matter. Hence, the phylogenetic diversity and distribution pattern of Planctomycetes in the surface sediments of a high Arctic fjord, the Kongsfjorden were studied. Further, considering the release of ammonium as a part of mineralization, the diversity of bacterial community involved in anaerobic ammonium oxidation (anammox) was also evaluated. The highly diverse Planctomycetes community, which consisted mainly of uncultivated and uncharacterized Planctomycetes, was observed in the study area with a total of 162 OTUs. The major genera observed were Blastopirellula (13.3%), Gimesia (13%), Rhodopirellula (10%), Planctomicrobium (2%) and Thermogutta (1.6%). Functional prediction revealed the dominance of carbohydrate metabolism genes and the presence of gene clusters for production of secondary metabolites and xenobiotic degradation. Anammox bacterial sequences were detected from all the samples with a total of 52 OTUs. Most of the OTUs belonged to the genus Candidatus Scalindua and three distinct clusters were observed in the phylogenetic tree, (a) Ca. Scalindua brodae (49%), (b) Ca. Scalindua wagneri (31%) and (c) Ca. Scalindua marina (12%) based on their phylogenic distance. Our findings suggest the existence of highly diverse Planctomycetes and anammox bacterial community with regional variants in the sediments of Kongsfjorden.

Metagenomic data of fungal community in Kongsfjorden, Arctic using Illumina next generation sequencing.

The data represents the diversity and distribution of fungal communities in Kongsfjorden, Arctic. The metagenomic DNA analysis was performed using next generation sequencing technology (Illumina MiSeq). Sequence data from amplified internal transcribed spacers (ITS) 2 region with fungal-specific primers exposed 83,417 sequences belonging to 7 operational taxonomic units (OTUs). Five of these OTUs belonged to Ascomycota, and one each to Basidiomycota and unclassified group. Aspergillus, Candida, Emericella and Nakaseomyces were the different genera identified and they belonged to the fungal orders Helotiales, Eurotiales and Saccharomycetales. The data explored the presence of important fungal communities in the Arctic marine ecosystem. Metagenome data is now available at NCBI under the Sequence Read Archive (SRA) database with accession no. SRP152688.